This invention relates to wafer carriers, more particularly it relates to front opening wafer carriers with separable doors.
The processing of wafer disks into integrated circuit chips often involves several steps where the disks are repeatedly processed, stored and transported. Due to the delicate nature of the disks and their extreme value, it is vital that they are properly protected throughout this procedure. One purpose of a wafer carrier is to provide this protection. During processing of semiconductor wafers or magnetic disks, the presence or generation of particulates presents very significant contamination problems. Contamination is accepted as the single largest cause of yield loss in the semiconductor industry. As the size of integrated circuitry has continued to be reduced, the size of particles which can contaminate an integrated circuit has also become smaller, making minimization of contaminants all the more critical.
Wafer Carriers configured as enclosures for holding wafers intermediate processing steps are typically formed of numerous plastic components assembled together. The industry accepted configuration for larger wafers, that is 300 mm wafers, is to have an enclosure portion with a lower machine interface configured as a kinematic coupling, an open front closeable by a door, and stacked wafer shelves on the inside sides of the enclosure portion. A door with a pair of latching mechanisms sealingly closes the open front and will typically have wafer restraints that contact and restrain the forward edge of the wafers in the enclosure.
Conventional carriers used in the semiconductor industry may develop and retain static charges. Static buildup on carriers can cause semiconductor processing equipment to automatically shut down. It is desirable to have a carrier with static dissipation characteristics to control static charges.
A undesirable effect of static charges is exhibited when a charged plastic part comes into contact with an electronic device or processing equipment of a significant different potential it may discharge in a damaging phenomena known as electrostatic discharge (ESD). These discharges can be catastrophic during the processing of wafers into semiconductors. Means are known to provide grounding of wafers for minimizing the occurrence of such discharges. See for example U.S. Pat. No. 5,711,082 to Nyseth, owned by the owner of the instant invention.
Contaminants in the form of particles may be generated by abrasion such as the rubbing or scraping of the carrier with the wafers or disks, with the carrier covers or enclosures, with storage racks, with other carriers, or with the processing equipment. It is critical to keep contaminants off of the wafers. The polycarbonate plastic shell of wafer carrier enclosures are known to naturally have a slightly negative charge. Grounding of the wafer shelves and thus the wafers within the enclosure can render the wafers with no electric charge causing particles to be attracted to the plastic enclosure rather than the wafers. See U.S. Pat. No. 5,944,194 to Gregerson, Gallagher, and Wiseman, owned by the owner of the instant invention. The U.S. Pat. No. 5,711,082 and 5,944,194 patents are incorporated herein by reference. These references provide background information, as well as the configuration and construction of wafer carriers, and illustrate means of conventionally providing paths to ground.